Tension adjusting device for sewing machine belts



A. GORDON March 8, 1938.

TENSION ADJUSTING DEVICE FOR SEWING MACHINE BELTS Filed April 9, 1937 INVENTOR Patented Mar. 8, 1938- PATENT OFFICE TENSION ADJUSTING DEVICE FOR SEWING MACHINE BELTS Abe Gordon, New York, N. Y. Application April 9, 1937, Serial No. 135,850

2 Claims.

This invention relates to an improvement in tension adjusting devices for sewing machine belts and has for its object the provision of a device which will provide a uniform tension on belts of this character to thereby insure not only satisfactory operation of the machines driven by the belts, but tend to avoid belt slippage, vibration, increase the life of the belts and generally improve operating conditions.

Sewing machines of the kind conventionally used in clothing manufacturing establishments are arranged on opposite sides of a lengthy table beneath which a power-driven shaft is mounted. The sewing machines are all driven in the same direction by round belts which extend over pulleys secured on the shaft and which connect with coned pulleys which drive the sewing machine shafts through a clutch connection. The coned pulleys are usually caused to drive the sewing machine shafts by the movement of a knee lever which causes engagement of the clutch. The belts which connect with the power shaft often tend to stretch after a short period of use, thereby requiring their removal from the machine and the severance of a belt section, then the recoupling of the ends of the belt and the replacement on the machine. This causes considerable waste of time. Furthermore, a loose belt results in a loss of driving power and also causes the machines to run at varying speed.

The primary object therefore, of this invention is to provide means for applying a uniform tension on the belts to thereby take up any slack created by the stretching of the belts; to avoid friction, particularly in case of a belt in crossed position, and to control vibration of the belt and thus greatly smoothen the driving of the machine.

In the accompanying drawing, wherein an embodiment of the invention is shown, Fig. 1 is a sectional view through a sewing machine table showing the improved tension-adjusting device; Fig. 2 is a sectional view on the line 22 of Fig. 1, looking in the direction of the arrows; Fig. 3 is a sectional view on the line 3--3 of Fig. 1, looking in the direction of the arrows, and Fig. 4 is a sectional view through the pivot for the pulleyholding lever.

In Fig. 1 is shown the conventional long table I on the opposite longitudinal sides of which are mounted the sewing machines 2 and 3. Sewing machine 2 has the usual coned pulley 4 mounted beneath the table; the machine 3 being provided with a similar coned pulley 5. By suitable clutch mechanism, not shown, but conventional in sewing machines of this character, the coned pulleys are coupled with the drive shafts of their respective machines by operation of a knee or foot lever. At 1 is shown the power shaft, located below the table I and extending for the length of the table. Said shaft carries the pulley 8, over which the round belt 9 extends, said belt being crossed and extending over the'coned pulley i. Pulley 8 also carries another similar belt In which is not crossed and extends over the coned pulley 5. It will be clear from the foregoing that by rotation of the power shaft I, both sewing machines will, by means of the belt drives shown, be driven in the same direction.

The table I is mounted upon a suitable frame which includes the legs H connected by the cross braces l 2. Secured on the lower cross brace by means of bolt I3 is an angular fixed supporting bracket M, the bolt extending through the vertically disposed portion of said bracket. The horizontal portion l5 of the bracket is slotted at IE to receive bolts IT to hold another bracket H] on bracket l4. Bracket I8 has a footportion l9 sloted at 20 to receive the bolts ll. Through the slotted arrangement of the two brackets 14 and I8- it will be understood that bracket I8 is adjustable to and from fixed bracket l4 for a purpose to be hereinafter set forth. The upper end of the vertical portion of bracket I8 carries a bell crank lever 2| which is pivoted on a bolt 22 extending through bracket 48. The lever 2| is spaced away from bracket l8 by means of the nut 23 and washer 24. A tension spring 25 surrounding bolt 22 exerts a resilient pressure against a washer 26 which is forced against the face of lever 2|. Accordingly, the lever is mounted between the washers 23 and 26 and is resiliently held against washer 23 by the pressure of the spring 25. Spring 25 may be adjusted as to pressure or tension by adjustment of bolt 22 through bracket I8. One arm of the. bell crank lever Zl carries a rotatably mounted pulley 21 which engages against the belt 9. Bell crank 2| is preferably made of flat stock and its second arm is twisted as at 28 and an adjusting screw 29 extends through said portion 28. Screw 29 is provided with a wing nut 30 and it engages one end of a coil spring 3|, said spring having its opposite end secured to the foot portion IQ of bracket I8. By manipulation of the Wing nut 30, the tension of spring 3! can be regulated and consequently the pressure of pulley 21 against the belt 9 can be manually controlled.

From the foregoing, the operation of the improved tension a-djusting device will be readily understood. By means of the adjustment 30, the pulley 21 can be held in contact with the belt 9 with the desired tension sufficient to constantly take up slack in the belt at all times, the spring 3| normally holding the pulley against the belt.

and greatly smoothing out the operation of the belt over the pulleys. The coil spring surrounding bolt 22 and operating against lever 2| tends to dampen out lateral vibration of the belt 9 as the same runs at high speed. Said spring 25 also takes up any play due to Wear at the pivot point of the lever 2|. ment of the bracket I Bpermitting the bracket to be adjusted to and from the supporting bracket l4 enables the tension device to be so adjusted that the crossed portions of the belt will be held by pulley 21 out of contact with one another and friction or the rubbing of one section of the belt against the other may be thus avoided.

The device is highly flexible in operation and the manner in which .it is resiliently mounted, namely by cooperation of the springs 3| and'25,

enables it to not only take up slack in the belt.

at all times, but dampens lateral vibration, which it has been found tends to cause considerable wear and tear on belts of this character.

In'the case of the uncrossed belt 10 on the opposite side of the machine, a slightly different mounting is shown. There, the lower cross member l2 of the frame supports bracket by means of the bolt 3|, said bracket holding .another bracket 32. Bolts 33 adjustably secure bracket 32 to the supporting bracket 30 in the manner heretofore described with respect to brackets I4 and la. The resilient pivot arrangement described with respect to the structure of Fig. 2 is the same in this embodiment, except that instead of a bell crank lever, the lever 34 is used. Said lever 34 receives the pivot bolt 22 at one of its ends and at its other end carries a rotatable pulley 35 which is drawn downwardly in contact with the upper reach of the belt ID by the coil spring 36 which has one of its ends attached to the stud 31 on lever 34 and has its other end attached to the end of adjusting screw 38 extending through the foot portion of bracket 32 and receiving a wing nut 39. The pressure of pulley 35 against the upper portion of belt I0 is regulated by means of coil spring 35in the manner described in respect to coil spring 3|.

By both arrangements shown, the tension of the belt is easily regulated and maintained so The slotted arrangethat slippage and wear of the belt is avoided. As' previously explained, the lateral vibratory movements of the belt while running at-high speed are resiliently checked or dampened by means of the coil spring 25 and the frictional action of the sides of the belts against all of the pulleys with which they contact is greatly minimized so that wear of the belt is accordingly reduced and its life materially increased. Through the use of these devices, the machineruns with exceptional smoothness and jerkiness and slipping of the belt in starting is completely eliminated.

What'Ifclaiin is:

1. A device of the character described comprisinga power shaft provided with a pulley, a sewing machine having a drive pulley, a belt connecting said pulleys, a support, a shaft adjustably anchored at one end in the support, a

lever pivotally and slidably mounted on said shaft for movement laterallyof the support and said belt, resilient means on said shaft engaged with an abutment at the outer end of the shaft .and engaged atits'other end with said lever for resilientlyresisting vibratory movement of said lever axially of said shaft and permitting free pivotal movement of said lever on said shaft, a pulley'on said lever held in contact with the belt, a spring for holding said pulley against the belt and means for adjusting the tension of said spring.

2. A device of the character described comprising a power shaft provided with a pulley, a sewing machine having a drive pulley,-. a belt extending between and riding over said pulleys, a support, a shaft adjustably anchored at one end in the support, a bell crank lever pivotally and slidably mounted on said shaft for movements axially of said shaft and laterally of said belt, a coil spring surrounding the shaft engaged with an abutment at the outer end of the shaft and engaged at its other end with said bell crank lever for regulating'the axial movement of said lever on said shaft and permitting free pivotal movement of said lever on said shaft, a pulley at one end of said bell crank lever held in contactwith said belt and a spring connected at one end to the other end of said'bell crank lever and adiustably connected at its other end to said sup-. port for resiliently holding the pulley against the belt.

' ABE GORDON. 

